Temperature and Global Warming

Temperature and Thermometry

• The average temperature of the surrounding environment needs to be around 82℉ (28℃) to maintain the body's temperature without external devices.
• High environmental temperatures can be dangerous to the body, causing heat cramps, exhaustion, and stroke.

Global Warming

• One of the most immediate effects of global warming is the increase in temperatures worldwide.
• The average global temperature has increased by about 1.4 degrees Fahrenheit (0.8 degrees Celsius) over the past 100 years.
• 2016 was the hottest year on record, with a global temperature 1.78 degrees Fahrenheit (0.99 degrees Celsius) higher than usual.

Greenhouse Effect

• The natural warming of the Earth occurs when greenhouse gases in the atmosphere trap heat from the sun.
• The greenhouse effect is important for warming the planet to a comfortable average temperature (15℃) and supporting life on Earth.
• Human activities, such as burning fossil fuels for energy, are increasing the natural greenhouse effect, leading to global warming.

Measuring Temperature

• Thermometers measure temperature in degrees.
• There are three different temperature scales: Centigrade (Celsius), Fahrenheit, and Kelvin.
• The Celsius scale is commonly used for scientific works and has greater scientific significance.
• The Kelvin scale is used to define the zero point (0K or -273.15℃) as the lowest possible temperature.

Types of Thermometers

• Liquid Thermometers:
  • Mercury thermometers can measure temperatures between -30℃ and 300℃ and are used in households, laboratories, and industries.
  • Alcohol thermometers can measure temperatures from -115℃ to 78.15℃ and are popular due to their non-toxicity.
• Resistance Thermometers:
  • Made from platinum wire, they measure temperature by changing resistance.
  • Used in a wide temperature range (-270℃ to +700℃).
• Thermocouples:
  • Consist of thin wires of different metals, welded together at the ends to form two junctions.
  • Measure temperature by generating a voltage dependent on the difference in temperature between the junctions.
  • Can measure temperatures as high as 2300℃ or as low as -270℃.
• Thermistors:
  • Resistance thermometers whose resistance is dependent on temperature.
  • Made of metallic oxides, pressed into a shape and encapsulated with an impermeable material.
  • There are two types: Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC).
  • Typically, thermistors achieve high precision within a limited temperature range of about 50℃ around the target temperature.
• Radiation Thermometers:
  • Measure temperature by using electromagnetic radiation from a body.
  • Not based on any change of property with temperature.